Considerations for standardizing qpcr assays.

Transcription

1 Considerations for standardizing qpcr assays. qpcr Satellite Symposium BioCity Leipzig March 10-11, 11, 2005 Reinhold Mueller, PhD Senior Staff Scientist

2 Outline: Introduction Controls, references and standards in qpcr The importance of standard curves Confidence intervals and data comparison Uses for natural reference RNA Uses for synthetic reference RNA

3 Introduction

4 In order for a scientific result to be valid an independent person who is skilled in the art must be able to reproduce it.

5 A typical qrt-pcr protocol: Select cells or tissue of interest Extract total RNA Reverse transcribe RNA using random primers Determine RNA concentration, if possible Quantify each gene of interest relative to a standard curve using QPCR Express data normalized to input RNA and relative to a control sample

6 Control Reference - Standard Individual Reaction Assay Global Comparison

7 Variability in Determining Initial Target Concentration Assuming that the same qrt-pcr reagent and platform used to amplify and detect the same RNA target on different days will give the same result might be wrong. There is an inherent variability in each of the necessary components, which are: Instrumentation Reagents Template Operator Analysis

8 PCR Amplification PCR: Correlation of amount of amplified DNA to amount of initial target DNA Y=X (1+ E) n Y = X = E = n = PCR amplified quantity target DNA quantity prior to PCR amplification efficiency number of cycles

9 Intra-Laboratory Variability <Ct> (run) Ct control chart Run LCL <Ct> UCL The lower confidence level (LCL) and the upper confidence level (UCL) were calculated for the measured Ct-The target is TBP and the template is 100 ng QPCR Reference Total RNA

10 Determination of RNA Concentration A260/A280 NanoDrop Agilent Bioanalyzer RiboGreen

11 RNA quantification Agilent Ribogreen UV Spec Nanodrop

12 TaqMan chemistry Probe Target and enzyme Hydrolysis

13 SYBR Green I Chemistry dsdna + SYBR Green I Binds groove

14 Amplification Plot Terms plateau Fluorescence baseline threshold dr Ct Cycle Number

15 Amplification Plot GUS - 4x Dilution, starting at 1000 ng (linear/linear) Fluorescence ( (drn drn) Cycles

16 Standard Curve Quantitation Versus Comparative Quantitation Standard Curve Quantitation: Gene of interest (GOI) Normalizer Passive reference dye Relative Comparison: Gene of interest Normalizer Calibrator Passive reference dye

17 Controls, references and standards in qrt-pcr

18 Controls for Quantification Using Comparative and Standard Curve Methods Reverse Transcription Controls PCR Controls Operator Controls Controls for Instrumentation

19 Testing of different DNase treated Mouse RNA for DNA contamination using TNFα Intron 1 primers. 50ng Mouse DNA 50ng Mouse RNA 25U for 15min 50U for 5min SYBR Green I Dissociation Profile SYBR Green I Amplification Plot

20 Standard curve: copies SYBR Green, Alien RNA Template; 50nM of each forward and reverse primer 100 copies 10e8 copies 10 copies One NTC (Ct = 38)

21 Dissociation Curve for Alien RNA Amplicon Alien RNA samples NTC

22 References for Quantification Using Comparative and Standard Curve Methods Endogenous Reference Exogenous Reference Calibrator

23 Relative Quantification of PMCA 1 mrna Relative Quantity Ionomycin PMA+Ionomycin Treatment Target is PMCA 1; SYBR Green I detection; Normalizer is β2-microglobulin; Calibrator is total RNA from untreated Jurkat cells; Experimental RNAs are from Jurkat cells treated with Ionomycin,, or treated with Ionomycin/PMA.

24 Standards for Quantification Using Comparative and Standard Curve Methods Standard Curves Natural Standards Un-natural natural Standards Standards for Instrumentation

25 QPCR Standards Microarray Analysis Reverse transcribed RNA dilution series (β-actin)

26 Variability in qrt- PCR assays can be assessed with a constant RNA target

27 The Template in a Universal Reference (Or Standard) for QPCR can be Total RNA Poly(A) n -containing RNA Synthetic RNA cdna

28 Quantitative PCR Human Reference Total RNA Good gene representation Precise determination of RNA concentration Extensive quality control Production in large batches Convenient buffer

29 High, Medium and Low Abundant Targets Analyzed with TaqMan Probes (PDARs ( PDARs) β 2-Microglobulin Lot 1 Lot 2 100ng ng ng ng NTC no ct no ct TBP Lot 1 Lot 2 100ng ng ng ng NTC no ct no ct GUS Lot 1 Lot 2 100ng ng ng ng NTC no ct no ct IL-5 Lot 1 Lot 2 100ng ng NTC no ct no ct

30 Assay Validation

31 Assay Validation A SYBR Green I assay for PMCA 1 was validated using QPCR reference RNA. The reference gene was β2-microglobulin.

32 Assay Development

33 Relative Quantification with QPCR Reference RNA Relative Quantity Jurkat Ionomycin PMA+Ionomycin Treatment Target is PMCA 1; SYBR Green I detection; Normalizer is β2-microglobulin; Calibrator is QPCR Reference Total RNA; Total RNA from untreated Jurkat cells, treated with Ionomycin,, or treated with Ionomycin/PMA.

34 Relative Quantification of PMCA 1 mrna Relative Quantity Ionomycin PMA+Ionomycin Treatment Target is PMCA 1; SYBR Green I detection; Normalizer is β2-microglobulin; Calibrator is total RNA from untreated Jurkat cells; Experimental RNAs are from Jurkat cells treated with Ionomycin,, or treated with Ionomycin/PMA.

35 Assay Standardization

36 Microarray Analysis Amplification Plot GUS - 4x Dilution, starting at 1000 ng (linear/log) Fluorescence ( (drn drn) Cycles

37 Standard Curve GUS - 4x Dilution, starting with 1000 ng Ct (drn) Initial Quantity (nanograms)

38 Standard Curve Cyclophilin - 1.3x Dilution, starting with 100 ng Ct (drn) Initial Quantity (nanograms)

39 Describing a Standard Curve 1. Linear Range 2. Standard deviation of replicates and R 2 -value 3. Confidence interval 4. Slope of the best-fit line 5. Y-axis Y intercept

40 Mathematical Model for Comparison of Two QRT-PCR Runs Decide on number of replicates. Generate a standard curve with QPCR Reference Total RNA. Calculate Confidence Intervals (CI). Compare quantities from runs on different days or on different platforms. Apply modified t-test. t test. Decide if the two Unknown quantities were different.

41 Comparing Initial Target Concentration Acquired on Two Different Platforms gus comparison runs (99%CI) Starting qty Std qty B01 UCL B01 LCL B01 unk B01 UL B01 LL Std qty 7700 UCL 7700 LCL 7700 Unk 7700 UL 7700 LL Ct 7700 Mx4000 B01 Ct 1 n St Qty Ct 2 n St Qty ratio 1-(p) Different? unk % Not sure unk % Not sure unk % YES!

42 Synthetic reference RNA

43 Alien RNA standard curve ( copies) SYBR Green, 100nM of each forward and reverse primer 10 8 copies 10 copies NTC

44 Dissociation Curve 10 copies NTC

45 Standard Curve ( copies) of Alien RNA using 100nM of each primer

46 Spike in ng Human Brain RNA into Alien RNA (10 5 copies) Spike in1000ng of Human RNA

47 Summary

48 Acknowledgements Gothami Padmabandu Mary Salehi Natalia Novoradovskaya Roger Taylor Tania Nolan